1. Field of the Invention
The present invention relates to a washer, and more particularly, to a method and apparatus for controlling a drum-type washer storing a set of eccentricity detection reference values that are selectable at the time of wash course selection to perform a dewatering cycle as desired.
2. Discussion of the Related Art
A drum-type washer uses the drive force of a motor to perform sequentially washing, rinsing, and dewatering cycles by rotating an inner tub with respect to an outer tub accommodating a load of laundry and water. The structure of a general drum-type washer is shown in FIG. 1.
Referring to FIG. 1, a drum-type washer comprises a tub 2 suspended within a body 1 by a damper 7 and a spring 6, a cylindrical drum 3 rotatably provided within the tub centering on a horizontal axis, and a drum motor 5 coupled with the drum via a drum shaft 4. The drum motor 5 is provided behind the tub 2 and includes a rotor 5b and a stator 5a. The drum shaft 4 is rotated together with the drum 3 and is directly connected to the rotor 5b to transfer directly a drive force of the rotor to the drum 3, which is provided with a plurality of lifters 3a installed axially on its inner surface. A door 8, opposing a forward opening of the drum 3, is provided to a predetermined portion of a front side of the body 1, and a gasket 9 for sealing the drum is provided between the door and drum. A control panel 10, disposed above the door 8, is provided to enter user commands for controlling washer operation.
In the above drum-type washer, a wash cycle is carried out when a rotational force of the rotor 5b is transferred to the drum 3 via the drum shaft 4, so that laundry within the rotating drum 3 is lifted by the lifters 3a and then falls by gravity. After completion of the wash cycle and a predetermined number of rinse cycles, a dewatering operation is performed by a high-speed rotation of the drum 3, which generates a centrifugal force while the water is drained from the tub 2. The rotational speed of the drum 3 depends on the drive of the drum motor 5, which is driven at a low rotational speed in a washing mode but is driven at a high rotational speed for dewatering.
Referring to FIG. 2, illustrating motor speed over time during a dewatering cycle as above, dewatering is performed according to a dewatering algorithm as a series of untangling steps followed by an intermittent dewatering stage including at least first and second intermittent dewatering periods with eccentricity detection being performed before and after each period to determine whether to accelerate the drum motor 5 for high-speed rotation for entering the main dewatering stage. In each untangling step, the rotational speed is approximately 70 rpm for a predetermined time to untangle the laundry, after which the first eccentricity detection is performed by holding the speed at about 108 rpm for a predetermined duration to steady the rotation. Thereafter, the first intermittent dewatering period of the intermittent dewatering stage is entered by accelerating to, say, 170 rpm, whereby partial dewatering and some amount of laundry settling occurs before decreasing the rotational speed back down to an eccentricity detection speed to perform another (i.e., the second) eccentricity detection. If the eccentricity detection determines that a state of unbalance is still present, a second intermittent dewatering period is entered by accelerating to a higher speed, say, to 300 rpm, whereby additional dewatering and laundry settling occurs before performing yet another (i.e., the third) eccentricity detection is performed. Assuming that the eccentricity detection shows an acceptable degree of balance in the rotating drum, such that high-speed rotation without excessive noise or vibration or undue loading can occur, an acceleration to as high as 600 rpm or more is achieved to perform the main dewatering under normal conditions, which may include further acceleration to 800 rpm before a predetermined dewatering time expires.
Eccentricity detection, which may be peculiar to an installation environment or operational habits, is performed by comparing a detected eccentricity with an eccentricity detection reference value stored in a lookup table and is referenced according to a detected laundry amount at the beginning of a selectable wash course. If the eccentricity detection reference value is too low, it may be difficult to enter the main dewatering stage. On the other hand, if the eccentricity detection reference value is too high, the ensuing levels of noise and vibration are likely to be excessive.
In the dewatering algorithm of the related art drum-type washer as described above, the lookup table storing the eccentricity detection reference value is set by the manufacturer of the drum-type washer. The eccentricity detection reference values of such a lookup table, however, may be unsuitable for a particular installation environment or the operational habits or preferences of a particular.